This is a long-term, open-label study of the safety, tolerability and effectiveness of RP103 in cystinosis patients who are naïve to any form of cysteamine treatment. Subjects will receive RP103 treatment for at least 12 months. US subjects will transition to the commercially approved drug PROCYSBI®. In Brazil, after at least 12 months of study participation and upon approval by the Brazilian regulatory authorities, subjects will be eligible to transition to a post study drug supply program, and continue to receive the drug at no personal cost.